Apparatus of this kind is already known which has a normally open inlet valve located in the pressure medium line between the main cylinder and the wheel brake cylinder, and a normally closed outlet valve located between the wheel brake cylinder and a pressure medium container. While these two valves represent the primary components of the anti-locking system, the wheel brake cylinder can be additionally exposed to pressure medium via a normally closed valve for purposes of propulsion control.
With a view to desired mass production of combination anti-locking systems and propulsion control systems, the known apparatus proves to be too complicated and thus too expensive. Furthermore, the valve for propulsion control and the inlet valve of the brake system are disposed in parallel in the known system, so that safety problems can occur under some circumstances.